Resilient inner conductor support



March 12, 1968 D. N. SEWELL 3,373,242

RESILIENT INNER CONDUCTOR SUPPORT Filed Feb. 15, 1967 3 Sheets-$heet lMarch 12, 1968 p.51. SEWELL RESILIENT INNER CONDUCTOR SUPPORT 3Sheets-Sheet 2 Filed Feb. 15, 1967 March 12, 1968 D. N. SEWELL 3,373,242

RESILIENT INNER CONDUCTOR SUPPORT Filed Feb. 15, 1967 r 3 Sht$-3heet iUnited States Patent 0 19 Claims. (Cl. 174-41 ABSTRACT 0F THE DISCLOSUREA resilient inner conductor support for use in coupling adjacent,axially-spaced inner conductor sections of a coaxial transmission lineto allow, and provide mechanical and electrical compensation for,relative movement between the various portions of the transmission line.Each support includes rigid coupling rings secured to the ends ofadjacent inner conductor sections and a relatively rigid berylliumcopper connector located therebetween. No portion of the supportprotrudes beyond the outer circumference of the inner conductorsections. Each connector has a ring-shaped base of smaller diameter thanthe inner conductor sections and two, axially-spaced, flexible discportions extending radially outwardly from the base, thereby defining anannular space, channel shaped in cross-section, for receiving adielectric support that maintains the inner and outer conductors incoaxial relation. A flange at the outer circumference of each discportion is secured to the adjacent coupling ring. In one disclosedembodiment, the connector is constructed of several circumferentiallyspaced, arcuate, channel-shaped in cross-section beryllium copperconnector portions, each of which has a number of relief slots extendingthrough its base portion and radially outwardly therefrom.

Summary of invention This invention relates to electrical transmissionlines and more particularly to coaxial transmission lines that transmitelectrical energy at microwave frequencies and to compensationstructures for use in such coaxial lines. This application is acontinuation-in-part of my copending application, Ser. No. 555,147 filedJune 3, 1966.

in high power coaxial transmission lines, such as those employed in highspeed search radar systems, internal loadings are imposed on the innerconductor sections. In conventional coaxial line design the anchorconnector and the inner conductor is employed to accommodatedifferential expansion and external forces imposed on the line. Theresulting wear or chafimg at the slip connection, however, reduces thecontact quality which promotes resistance heating, causing relaxation ofthe expansion springs, build up of resistive oxides, and allows seriesarcing to occur which very rapidly destroys the joint and contaminatesthe adjacent transmission line with the residue. Also, the production ofmetallic particles may seriously degrade the electrical quality of thetransmission lines. Such conductor slipping also generates electricalnoise which can significantly impair the quality of electrical signaltransmission in the system.

It is an object of this invention to provide a novel and improvedcoaxial electrical transmission line in which slippage between the innerconductor sections and other components of the line is essentiallyeliminated.

Another object of the invention is to provide a novel and improvedcoaxial support structure for a coaxial transmission line that providescompensation for differential movement between the two conductorelements of the line.

Still another object of the invention is to provide a novel and improvedinsulator spacer support structure that permits differential movementbetween the inner and outer conductors of the coaxial line withoutadversely affecting the electrical characteristics of the transmissionline.

In accordance with the invention, there is provided a compensationstructure for a coaxial transmission line that includes tubular innerand outer conductors. The compensation structure is arranged forconnection between adjacent sections of the inner conductor andpreferably receives an insulator spacer such as a disc of dielectricmaterial, so that it functions as a support structure to maintain theinner and outer conductors in coaxial relation. The compensationstructure comprises two flexible, electrically conductive transitionportions of disc configuration that extend radially outwardly to amaximum circumference that equals the outer circumference of the innerconductor and in opposite axial directions from a base portion to therespective sections of the inner conductor. These transition portionspermit the inner conduct-or sections to move towards and away from oneanother without any modification of the electrical conductivity of theinner conductor and thus provide compensation for mechanical stress towhich the transmission line is subjected. In a preferred embodiment, theringshaped compensation structure comprises a plurality of arcuatetransition portions of generally channel-shaped cross-section, each ofwhich extends radially outwardly from its base and in opposite axialdirections at its outer circumference. The channel base and sides ofeach transition portion may include a plurality of relief slots toprovide for radial movement of the channel base in an elec tricalcompensation action in addition to axial movement of the structure inresponse to the differential movement of the inner and outer conductors.

In a particular embodiment a series of sections of inner conductors areassembled with flexible insulator support structures connecting adjacentsections of the series. This assembled length of inner conductorsections is inserted within an outer conductor section that has a lengthsomewhat less than the inner conductor assembly in relaxed condition. Ananchor insulator is secured at one end of the outer conductor sectionand one end of the inner conductor assembly and then the next length ofinner conductor is assembled and the anchor insulator joining the twolengths of inner conductor assembly is fixed in place relative to theouter conductor so that the inner conductor is compressed axiallyloading the resilient support structures in their desired configurationand assuring a positive force condition on the conductor structuresthroughout its intended range of operation. In this assembly thedifferential movement compensation structures are preferably distributedalong the length of the inner conductor at the several resilientinsulator support structures. By appropriate design of the lengthrelationship between the inner and outer conductors, the desiredelectrical characteristics and compensation for mechanical expansionrequirements of the transmission lines are achieved. This structureprovides a sturdy support structure that is relatively easy toelectrically compensate and which provides a more rigid high powercoaxial transmission line which operates at high efiiciency over a largerange of internal loadings which might be imposed on the line andwithout the generation of significant electrical noise due to movementsof the several components of the line relative to one another.

Other objects, features and advantages of the invention will be seen asthe following description of particular embodiments thereof progresses,in conjunction with the drawings in which:

FIG. 1 is a sectional view of a portion of a coaxial transmission lineconstructed in accordance with the invention;

PEG. 2 is a sectional view showing details of the insulator spacersupport structure employed in the embodiment shown in FIG. 1 in relaxedcondition;

FIG. 3 is a view similar to FIG. 2 showing the insulator supportstructure in compressed condition as occurs during use;

FIG. 4 is a sectional view of a modified form of a transmission line inemploying a second form of insulator support structure constructed inaccordance with the invention;

FIG. 5 is an exploded view of components of the support structureemployed in the line shown in FIG. 4;

FIG. 6 is a sectional view showing details of the support structureconstruction of the type illustrated in FIGS. 4 and 5;

FIG. 7 is a sectional view of another form of support structure that isslightly different from that structure shown in FIGS. 4 to 6;

FIG. 8 is a sectional view of a transmission line employing a third formof insulator support structure constructed in accordance with theinvention;

FIG. 9 is a sectional end view of the structure taken along line 9 9 ofFIG. 8;

FIG. 10 is a perspective view of a component of the support structureshown in FIG. 8; and

FIGS. 11 and 12 are diagrammatic plan views of components of thestructure shown in FIG. 8.

Description of particular embodiments With reference to FIG. 1 there isshown a coaxial transmission line having an outer conductor 10 made upof sections ltla, 10b, etc. and an inner conductor 12 which is made upof a plurality of sections 12a, 12b, 12c, etc. The sections Illa, 10b ofthe outer conductor are secured together with conventional flangestructures 14 while the sections of the inner conductor 12 are connectedtogether with coupling structures 16, each of which receives andsupports a disc insulator 18 which provides support for locating theinner conductor 12 in coaxial relation to the outer conductor to.

The construction of the insulator disc support which connects adjacentsections of the inner conductor together may be better understood withreference to FIGS. 2 and 3. That structure includes a rigid base element20 in the form of a copper bushing which has a centrally located spacerridge 22 and a recessed seat surface 24, 26 on either side of ridge 22.Secured to each surface 24, 26 is a beryllium copper flexible discstructure 30, 0.032 inch in thickness that includes a flange portion 32extending in one direction at its inner periphery and a second flangeportion 34 extending in the opposite direction at its outer periphery.The flange portions are formed in a flat disc and then the disc may besubjected to 600 F. for two hours in a heat treating operation. Thesetwo flange portions are connected by a generally radially extendingtransition portion 36. The inner flange portions 32 of each disc aresilver soldered to the corresponding surfaces 24 and 26 of the bushingbase member 20 so that those flanges are in substantially the same planeas the surface of ridge 22.

The outer flanges 34- are similarly silver soldered to copper ringstructures ll? which function as mating connectors for receiving thesections of the inner conductor 12. Each ring 46 is of similarconfiguration to bushing 20 but of larger diameter and has a surface 42on which the flange 34 is secured, a surface 44 on which the end of thattubular inner conductor 12 is secured as by brazing or silver soldering,and a spacer ridge 46, the surface of which is flush with the outersurfaces of conductor 12 and flange 34 in assembled condition.

An insulator disc member is is mounted on this support structure, forpositioning between the inner and outer conductors after assembly of thecompensation structure has been completed.

The assembled length of inner conductor with disc insulators 13positioned on it has secured to either end anchor insulator structures59 which cooperate with the flange 14 via disc insulator supports 52 tolock the inner conductor section rigidly relatively to the outerconductor at that point. in the H8. 1 arrangement the disc 52 is rigidlysecured at its outer periphery between the elements of flange structure14 which are secured together by bolts and its inner periphery isclamped by the base as of the anchor support structure. These supportstructures may be of conventional configuration. The left anchorinsulator support structure, it will be noted, projects beyond the endor" the outer conductor in when the inner conductor 12 is in relaxedcondition. When the next length of outer conductor is clamped to theflange 1d it forces the disc insulator 52 carried by the anchorstructure base 56 to the right compressing each support structuresubstantially to the position shown in FIG. 3 so that the entire innerconductor structure is placed under a degree of axial compression. Theassembly when complete provides a rigid structure suitable for carryinglarge amounts of power and may be subjected to large mechanical loadingssuch as are encountered in a high speed search radar system withoutintroduction of electrical degradation, due either to change in theelectrical characteristics of the line under the applied loadings, tothe production of metallic dust, or noise generated as a result of themovement of one component of the transmission line relative to theother.

A second embodiment of the invention is shown in FIGS. 4 6 in whichsimilar reference numerals are used to denote similar structuralelements, with a prime being utilized to denote the modified structure.As will be seen in FIGS. 46 the insulator support structure includes asimilar rigid ring 20' that has a central ridge 22' and two supportsurfaces, 24' and 26. Flexible discs 3% each have an inwardly turnedflange 32 at its inner periphery and an outwardly turned flange 34' atits outer periphery which are connected together by the radiallyextending wall portion 36. The inner flange 32 is received on thesupport surface 24 in a similar manner to embodiment shown in FIGS. 1-3while a different type of connector structure 4&3 is employed to couplethe support structure to the inner conductor of the transmission line.This connector structure is made in two sections 60, 62 which havemating saw tooth surfaces 64-, 66. Holes 68 are drilled through eachsection and when the two sections are assembled together as shown inFIG. 4, these holes are aligned so that a suitable fastener such as abolt 70 (FIG. 7) may be passed through the two sections to secure thosesections together. Section 60 includes an annular surface 42' on whichouter flange 34' of disc 3% is secured. Section 62 has a similar annularrecessed surface 44 which receives the end '72 of the inner conductor12' in a manner similar to that shown in FIG. 2.

The use of this resilient support structure in an anchor insulatorconfiguration is shown in FIG. 6. In that figure, the inner periphery ofan insulator disc 52' is received in supporting relation within therecess formed by the base 22 of the support structure 20 and the flangeportions 32' of the flexible disc members 30. One disc is secured to sawtooth connector member 6% that has an axially extending hole through itwhile the other flexible disc is connected to the anchor insulatorstructure that includes coupling member 82, spacer ring 84, and a secondcoupling member 36. Member 82 has an annular recessed surface 88 at itsend which receives the flange 34- of a flexible disc so that a smoothcontinuous surface with the outer diameter of the inner conductor 12' isprovided. The spacer ring 8- which has been machined to a lengthsuitable to match the overall length of the outer conductor assembly tothe inner conductor assembly, is disposed between the two couplingmembers 82, 86. An

aligning pin 90 is utilized to define the proper relation between thosetwo coupling members and the structure is assembled together by a bolt92 which passes through the aperture in coupling section 60 to securethe anchor support structure together.

The flange assembly which receives the anchor insulator 52 at its outerperiphery and also secures the adjacent sections of the outer conductortogether includes two flange members 100 and 102 which are securedtogether by a bolt 54' and may include seal member 104 between them toseal the transmission line so that a pressurized gas may be used withinthe transmission system if desired.

A view of an intermediate support structure of the type employing twosaw tooth coupling members for use in the transmission line shown inFIG. 4 is shown in greater detail in FIG. 7.

A third embodiment of the invention is shown in FIGS. 8 through 12 inwhich similar reference numerals are used to denote similar structuralelements, with a double prime being utilized to denote the modifiedstructure. As will be seen in FIGS. 8 and 9, the insulator supportstructure includes a ring-shaped compensation structure 30" interposedbetween sections 12g and 121" of an inner conductor approximately 4inches in diameter. As shown, structure 30 comprises a plurality ofcircumferentially spaced, beryllium copper arcuate transition portions31a, 31b, etc., each of which has a substantially channel-shapedcross-section, including a pair of disc portions 36" extending radiallyoutwardly from a base portion 32" having a radius of approximately 2.75inches, to a maximum radius substantially equal to the outer radius ofthe inner conductor, and a pair of outer flanges 34" extending axiallyin opposite directions from the outer periphery of disc portions 36".The thickness of base portion 32", flanges 34" and disc portions 36" is0.031 inch.

As shown more clearly in FIG. 10, each transition portion 31 includes aplurality of relief slots 33 approximately 0.020 inch wide extendingthrough base portion 32" and radially outwardly through a major portionof the radial width of disc portions 36".

The outer flanges 34" of each transition portion 31 are silver solderedto copper ring structures 40 which function as mating connectors forreceiving the sections of the inner connector 12". Each ring 40" has acircumferential, axially-facing groove 41, 0.13 inch deep, in which theflange 34" is secured, a surface 44" on which the end of the adjacenttubular inner connector 12" is secured as by brazing or silversoldering, and a spacer ridge 46.

An insulator disc 18" is mounted on this support structure forpositioning between the inner and outer conductors after assembly of thecompensation structure has been completed. When several conductorsections are assembled, as in FIG. 1, each support structure iscompressed from the position shown in FIG. 12 to substantially theposition shown in FIG. 3 so that the entire inner conductor structure isplaced under a degree of axial compression. As shown in FIGS. 11 and 12,the differential movement between axially adjacent conductor elements ofthe inner conductor line which is accommodated by compensation structure30" results in axial movement of disc portion 36 and radial movement ofthe free base portion 32". It has been found that the small impedancechanges introduced by these coordinated axial and radial movements areto a large measure self-cancelling.

It is frequently desired to locate these resilient loading compensationstructures along the inner conductor assembly with non-uniform spacingso that the small impedance changes that may be introduced by thedielectric support elements 18 do not add cumulatively.

While particular embodiments of the invention have been shown anddescribed, various modifications thereof will be apparent to thoseskilled in the art and therefore 6 it is not intended that the inventionbe limited to the disclosed embodiments or to details thereof, anddepartures may be made therefrom within the spirit and scope of theinvention as defined in the claims.

What is claimed is:

1. A coaxial transmission line comprising a tubular outer conductor; atubular inner conductor having a plurality of axially aligned sections;a series of spaced connectors coupling adjacent sections of said innerconductor together,

each said connector providing an electrical connection between saidadjacent sections and including a base portion and two flexible,electrically conductive disc portions extending radially outwardlytherefrom and providing relatively rigid compensation for differentialmovement between the inner and outer conductors; and, dielectric spacermembers disposed between said inner and outer conductors for maintainingsaid conductors in coaxial coalition.

2. The transmission line as claimed in claim 1 wherein each saidconnector is substantially channel-shaped in crosssection and includes aplurality of relief slots extending through said base portion andradially outwardly therefrom through a portion of said disc portions.

3. The transmission line as claimed in claim 2 wherein each saidconnector includes a plurality of circumferentially-spaced arcuatetransition portions, each of said elements having a substantiallychannel-shaped cross-section.

4. The transmission line as claimed in claim 3 wherein each of saidarcuate transition portions includes at least one relief slot extendingthrough the base portion thereof and radially outwardly therefromthrough a portion of the radially-extending disc portions of saidtransition portion.

5. The transmission line as claimed in claim 4 wherein said transitionportions are relatively rigid elements of beryllium copper.

6. The transmission line as claimed in claim 1 and further includinganchor structures at spaced locations along said transmission line forcompressing the inner conductor sections axially relative to the outerconductor so that said radially extending resilient disc portions aremaintained under distorting force in normal use of said line.

7. The transmission line as claimed in claim 6 wherein a plurality ofsaid connectors are spaced along said inner conductor at randomintervals between said anchor structures.

8. The transmission line as claimed in claim 1 wherein said discportions are a relatively rigid element of berylliurrr copper.

9. The transmission line as claimed in claim 1 wherein said discportions form a smooth continuous surface with said inner conductors andno part of said disc portions protrudes beyond the outer circumferenceof said inner conductor.

10. The transmission line as claimed in claim 9 wherein said dielectricspacer members include a disc insulator support which is positionedbetween the spaced disc portions of a connector.

11. The transmission line as claimed in claim 10 wherein each saidconnector further includes a rigid support element of electricallyconductive metal and each said .disc portion has a first flange at itsinner periphery and a second flange at its outer periphery, said discportions being positioned on opposite sides of said support element withsaid first flanges secured in electrically conducting relation to saidsupport element and said second flanges secured in electricallyconducting relation to the correspending sections of said innerconductor.

12. A spacer support structure for use in a coaxial transmission linecomprising two coupling members of diameters corresponding to the innerconductor of said line and a ring-shaped, electrically conductiveconnector having a base portion of smaller diameter than said innerconductor and two flexible, electrically conductive disc portionsextending radially outwardly therefrom, each disc portion having anouter flange extending in one axial direction, each said flange beingsecured to the corresponding conductor coupling member, said conductiveconnector defining an annular space for receiving a radially extendingdielectric support member therein for providing support to maintaininner and outer conductors of a transmission line in coaxial relation.

13. The spacer support structure as claimed in claim 12. wherein saidbase portion comprises an electrically conductive base member and saiddisc portions each have an inner flange extending in the other directionfrom the outer flange of said disc portion, said inner flanges beingsecured in electrically conductive relation to said base member.

14. The spacer support structure as claimed in claim 12 wherein saidconnector is adapted to form a smooth continuous surface with said innerconductor such that no part of said disc portions protrudes beyond theouter circumference of the inner conductor to which they are to beconnected.

15. The spacer support structure as claimed in claim 1.2 wherein saiddisc portions are relatively rigid elements of beryllium copper.

16. The spacer support structure as claimed in claim 12 wherein saidconnector is channel-shaped in cross-section and includes a plurality ofrelief slots extending through said base portion and radially outwardlytherefrom through a portion of said disc portions.

17. The spacer support structure as claimed in claim 16 wherein saidconnector includes a plurality of circumferentially-spaced, arcuatetransition portions, each of said transition portions having asubstantially channel-shaped cross-section.

18. The spacer support structure as claimed in claim 17 wherein eachsaid transition portion includes at least one relief slot extendingthrough the base portion thereof and radially outwardly therefromthrough a major portion of the radially-extending flanges of saidtransition portion.

1'). The spacer support structure as claimed in claim 18 wherein saidtransition portions are relatively rigid elements of beryllium copper.

References Cited UNITED STATES PATENTS 3,327,257 6/1967 Weiss 174-28 X3,331,911 7/1967 Whitehead 174-28 X 2,774,944 12/ 1956 Lintzel 333-962,044,580 6/1936 Leach 333-% X 2,589,328 3/1952 Bondon 33396 FOREIGNPATENTS 74,178 5/ 1952 Denmark. 963,860 1/1950 France.

OTHER REFERENCES Cornes, R. W; A Coaxial-Line Support For 0 to 4000rnc., Proceeding of the Institute of Radio Engineers, vol. 37, No. 1,January 1949.

LARAMIE E. ASKIN, Primary Examiner.

A. T. GRIMLEY, Assistant Examiner.

